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H. C. ALLEN HIGH FREQUENCY AMPMFIER @my mwN N l wenn Feb. 18

.DMG .BNQ FON WN NN\ Horace Clifford HZZ l torucy -rl I IllhwA Feb. 18, v1941. H. c. ALLEN HIGH FREQUENCY AMPLIFIER Original Filed Aug. 29, 1936 2 Sheets-Sheet 2 All/9 Suventor Horacf.' Clifford HZZ/en/ 1w Gttorneg Patented Feb. 18, i941 OFFICE n tion' a pair oi curves and a. circuit diah are referred to in explaining another 20 e an circuit diagram of stili another will best be understood by refero Figures 3` and 4. In Figure 2 the 25 f ectivity curve for the tuned ine frequency transformer indicated at ry oaded y voltage is cause by he sp e c ar e e ct, e m a 0 ting resist her y the se- 0 eioud ei ctro s u in e cat o e l "e '1S made T39m-topped The CUYVG a 30 v t c th d nd varyi g m size selectivity ar t risti oi the with manges n mas the iiiae. @rm Wh th Cepam s m 1 i b p t a he pera n of 9, eluded i tr nsio m econdary v. C circuit in e beve-me tion d type of The Cep C 1 pr en 'n all mphers e 3v receiver vv 1 tend t de e the I, am hier cause oi the input capacity oi the amplifier tube. 35 'it i ect o riventio ovide an 1i the Capa @MOV d, S b king t e improved t vision s ort Wa e rad o receiver con g t mphfl T t be OTE nega-GWB oi the type h vm ther man i utomatic fOr the D il edv-Cine ga n the amvoiume or ga n nt Y he thereby duci he inp t capacity,

40 Mor specificaiiy, 1s a obiect ci my inventhe selectivity curve oi the i. F. transformer I o tion to provide an improved high frequency amiS 21S Sho by Y1 @u SWG S Ch Stages "ffr sn designed that its gai maybe varied are conn ct d n casca ,t overall selectivity the curv n "^^+inq its selectivity chaac- Characteristic '1S aS e viousiy such a selectivity characteristic is urimmme asit Aaccentuates the high irequenciea 5 '"Mre 3. the curve a is the sefrmer 4 hav- I claim as my invention:

1. A variable gain band pass ampliiier stage comprising a transformer having a primary and a secondary, said primary and secondary being so tuned and coupled as to have a double peaked selectivity characteristic in the absence of loading on the transformer, an amplifier tube having a plurality of electrodes including input electrodes, means for coupling said secondary across said input electrodes, means for varying the direct current potential applied .to one of said electrodes whereby the gain of said amplifier stage may be controlled, and means for so resistively loading both said primary and said secondary that the selectivity characteristic of said tuned transformer is substantially flat-topped, said primary and said secondary being resistively loaded unlike amounts, the ratio of primary loading to secondary loading being such that said selectivity characteristic remains substantially nat-topped during changes in said direct current potential.

2. The invention according to claim 1 characterized in that the ratio of one of said loadings to the other of said loadings is less than 3 to 1 and greater than 1 to 1.

3. The invention according .to claim 1 characterized in that the ratio of one of said loadings to the other of said loadings is oi the order of 2 to l.

4. A variable gain band pass ampliiier stage comprising a transformer having a primary and a secondary, said primary and secondary being so tuned and coupled as to have a double peaked selectivity characteristic in the absence of loading on the transformer, an amplier tube havmg input electrodes, means for coupling said secondary across said input electrodes, means for varying the direct current potential between the input electrodes of said tube whereby the gain of said amplifier stage may be controlled, and means for so resistively loading both said primary and said secondary that the selectivity characteristic of said tuned transformer is substantially attopped, said primary and said secondary being resistively loaded unlike amounts, the ratio of primary loading to secondary loading being such that said selectivity characteristic remains substantially flat-topped during changes in said direct current potential.

HORACE CLIFFORD ALLEN.

Feb. 1s, 1941.

l W. T. ALLEN so'LDERLEss CONNECTOR Filed Feb. 26. -1940 INVENTOR- e. BY Wal/ace fil/en i l W ATT RN 

